Top 10 facts about the world. A brain stem stroke is a stroke which originates in the brain stem. Because the brain stem handles many of the body's basic life support functions, such as breathing and heart rate, a brain stem stroke can be fatal.
The myofibrils are composed of actin and myosin filaments, repeated in units called sarcomeres, the basic functional units of the muscle fiber. The sarcomere is responsible for the striated appearance of skeletal muscle, and forms the basic machinery necessary for muscle contraction.keletal muscle is made up of individual muscle cells or myocytes, known as muscle fibers. They are formed from the fusion of developmental myoblasts (a type of embryonic progenitor cell that gives rise to a muscle cell) in a process known as myogenesis. Muscle fibres are cylindrical, and multinucleated.
A muscle fiber consists of a bundle of muscle myofibrils. 4. muscle myofibril = contains thousands of sarcomeres-sometimes as many as 10,000 sarcomere units end-to-end. 5. sarcomere = is the functional unit of a muscle contraction because it is this structure that actually shortens during a contraction.